A seven-day continuous intravenous infusion of cytosine arabinoside plus a 3-day schedule of intermittent daily doses of Adriamycin has been shown to be an effective chemotherapy for the induction of remission in adults with acute nonlymphocytic leukemia as the combination of cytosine arabinoside with daunorubicin. A complete remission rate of 65 percent has been obtained with this combination. At present it is too early to discern whether the addition of either neuraminadase-treated allogeneic myeloblasts or splenectomy to chemotherapy during remission maintenance treatment enhances the duration of remission or survival of patients. Serum muraminase levels appear to accurately reflect disease activity in a large proportion with acute nonlymphocytic leukemia. Carcinoembryonic antigen and serum immunoglobulin concentrations do not appear to accurately reflect disease activity, and biochemical testing of leukemic bone marrow cells also does not allow for selection of favorable groups of patients to be treated with either cytosine arabinoside or daunorubicin alone. Reverse transcriptase has been identified in the bone marrow cells of leukemia patients prior to treatment and in morphologically normal peripheral cells during complete remission. This may suggest that morphologically and functionally normal granulocytes in the peripheral blood of leukemia patients in complete remission may actually be derived from leukemic cells.